THAT munching sound you hear on stage? It’s not actors chewing the scenery, but rather eating their props.

Never has the phrase “dinner theater” seemed as apt as it has this season. Not only do sandwiches loom large in “The 39 Steps” and “Macbeth,” but there’s roast chicken and cannolis (“Top Girls”), scrambled eggs (“A Catered Affair”), ham and eggs (“The Adding Machine”) and what sounds like the world’s least appealing lasagna (“From Up Here”).

No wonder Julie White occasionally wishes she were in another show.

“Roast chicken might be doable,” concedes the star of “From Up Here,” about a dysfunctional family that spends a lot of time dining in.

“I push that lasagna around because I know it’s going to be cold and old – two things you don’t want to eat,” she says. “So I added a side salad to that picnic – some romaine lettuce.”

One of White’s co-stars, Jenni Barber, has it even worse in a scene set at a high school cafeteria.

“They’ve given her edamame,” White says, grimly.

“And when that edamame’s about five shows old, she stores them between her cheek and gum. As soon as she gets off stage, spits them out.”

Why bother? Theater people agree there’s nothing like real food – and the occasional fragrance of cooking eggs – to ground a play in reality.

Or, as White points out, “Food is a huge part of living, and eating meals together is such a loaded dramatic situation.”

The dining is particularly fraught in “A Catered Affair,” the new musical about a poor family in the ’50s.

Given that its director is John Doyle, the man who made Patti LuPone blow her own tuba, it’s no surprise to find Faith Prince’s beleaguered housewife scrambling eggs – and the man who plays her hubby, Tom Wopat, eating them for eight shows a week.

And to think, Prince says: Doyle once had her gutting fish, too.

“My hands smelled terrible,” she says. “I asked, ‘Do you really think this is the way to go?’ ” So farewell, fish – but the eggs remained.

“Don’t tell Tom,” she adds, “but occasionally I get a shell in there. Sometimes I can get it out, and sometimes I can’t.”

Nothing is left to chance at Broadway’s newest “Macbeth.”

Patrick Stewart’s murderous Scotsman carves up a sandwich, bites down and delivers, through a mouthful of bread and chicken, a muffled bit of the Bard.

It’s a shocking moment – one that seems artless not only because Stewart is superb, but because Reg Vessey is hard on the job.

“The bread was the thing,” says the veteran props man.

“They’d auditioned bread in other places, but the key is pumpernickel – a good soft pumpernickel holds itself with no crumbs.”

Every bite the actors eat – from cream-cheese canapes to chocolate cake – has been meticulously planned, says Vessey. He now buys pickles from a particular Vermont purveyor after Stewart recoiled from a store-bought spear.

“He came to me and said, ‘There’s a certain thing about a pickle,’ and I went, ‘Oops!’ That kosher dill pickle wasn’t what he was looking for.”

Overall, he says, the former “Star Trek” commander seems pleased.

“Early on in the run, he said, ‘Save the sandwich, I’m hungry,’ ” Vessey says. “To me, that’s a good sign.”